Nginx proxy_pass to a variable url

Question

I am new to Nginx. As I know, we can configure proxy_pass url in nginx.conf like:

location /test
{
     proxy_pass http://10.10.10.10:10000;
}

But now, I need to proxy_pass to a variable url, we could get this url in http request header or request body(for example).

How could I implement this? Thanks for any help!

EDIT 1(explain my question):

There is a http request with a param named "redirectUrl" in its header send to Nginx, I just want Nginx modify this http request header and then send this request to the redirectUrl. Because the redirectUrl is a variable, so I guess "proxy_pass $request" can implement this, but I don't know how. Who can give me a hint or is there any documentation?

EDIT 2：

I tried ngx_lua :

location /apiproxytest {

    set_by_lua $redirectURL '
            return ngx.req.get_headers()["Host"]
    ';

    header_filter_by_lua '
             ngx.header["RedirectURL"] = nil;
             ngx.header["Host"] = nil;
    ';

    echo "1:" $redirectURL;

    set_by_lua $redirectURL2 '
            return ngx.req.get_headers()["Host"]
    ';

    echo "2:" $redirectURL2;

    #proxy_pass $redirectURL;
}

I found that echo 1 and echo 2 were the same, as ngx.header.HEADER explains, ngx.header["Host"] = nil is supposed to remove Host in http request header. Why echo "2:" $redirectURL2 can also print the value of Host?

@AlexeyTen thanks for your help, I had read the documentation, but it only tell me can, there is no how. Can you give me a hand? — SomnusLee
– SomnusLee, Commented May 21, 2015 at 2:13

fannheyward · Accepted Answer · 2015-05-22 03:35:13Z

1

Try ngx_lua.

Get redirectUrl from ngx.req.get_headers in set_by_lua, then set to something like $redirectURL, finally proxy_pass $redirectURL.

Append for Edit 2:

Why echo 1 and echo 2 were the same?

This is caused by Nginx Phases

set or set_by_lua is working at rewrite phase, echo is working at content phase, header_filter_by_lua is working at output-header-filter phase (doc), which is behind content.

Your config is worked like this:

set_by_lua -> set_by_lua -> echo 1 -> echo 2 -> header_filter_by_lua.

edited May 22, 2015 at 3:35

answered May 21, 2015 at 2:19

fannheyward

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2 Comments

SomnusLee Over a year ago

Thank you! I have edited my new question of using ngx_lua. Please hlep me~

fannheyward Over a year ago

@SomnusLee I append my answer, wish to help you.

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